In robotically-assisted or telerobotic surgery, the surgeon typically operates a master controller to remotely control the motion of surgical instruments at the surgical site from a location that may be remote from the patient (e.g., across the operating room, in a different room or a completely different building from the patient). The master controller usually includes one or more hand input devices, such as joysticks, exoskeletal gloves or the like, which are coupled to the surgical instruments with servo motors for articulating the instruments at the surgical site. The servo motors are typically part of an electromechanical device or surgical manipulator (“the slave”) that supports and controls the surgical instruments that have been introduced directly into an open surgical site or through trocar sleeves into a body cavity, such as the patient's abdomen. During the operation, the surgical manipulator provides mechanical articulation and control of a variety of surgical instruments, such as tissue graspers, needle drivers, electrosurgical cautery probes, etc., that each performs various functions for the surgeon, e.g., holding or driving a needle, grasping a blood vessel, or dissecting, cauterizing or coagulating tissue.
The number of degrees of freedom (DOFs) is the number of independent variables that uniquely identify the pose/configuration of a telerobotic system. Since robotic manipulators are kinematic chains that map the (input) joint space into the (output) Cartesian space, the notion of DOF can be expressed in any of these two spaces. In particular, the set of joint DOFs is the set of joint variables for all the independently controlled joints. Without loss of generality, joints are mechanisms that provide, e.g., a single translational (prismatic joints) or rotational (revolute joints) DOF. Any mechanism that provides more than one DOF motion is considered, from a kinematic modeling perspective, as two or more separate joints. The set of Cartesian DOFs is usually represented by the three translational (position) variables (e.g., surge, heave, sway) and by the three rotational (orientation) variables (e.g. Euler angles or roll/pitch/yaw angles) that describe the position and orientation of an end effector (or tip) frame with respect to a given reference Cartesian frame.
For example, a planar mechanism with an end effector mounted on two independent and perpendicular rails has the capability of controlling the x/y position within the area spanned by the two rails (prismatic DOFs). If the end effector can be rotated around an axis perpendicular to the plane of the rails, there are then three input DOFs (the two rail positions and the yaw angle) that correspond to three output DOFs (the x/y position and the orientation angle of the end effector).
Although the number of non-redundant Cartesian DOFs that describe a body within a Cartesian reference frame, in which all the translational and orientational variables are independently controlled, can be six, the number of joint DOFs is generally the result of design choices that involve considerations of the complexity of the mechanism and the task specifications. Accordingly, the number of joint DOFs can be more than, equal to, or less than six. For non-redundant kinematic chains, the number of independently controlled joints is equal to the degree of mobility for the end effector frame. For a certain number of prismatic and revolute joint DOFs, the end effector frame will have an equal number of DOFs (except when in singular configurations) in Cartesian space that will correspond to a combination of translational (x/y/z position) and rotational (roll/pitch/yaw orientation angle) motions.
The distinction between the input and the output DOFs is extremely important in situations with redundant or “defective” kinematic chains (e.g., mechanical manipulators). In particular, “defective” manipulators have fewer than six independently controlled joints and therefore do not have the capability of fully controlling end effector position and orientation. Instead, defective manipulators are limited to controlling only a subset of the position and orientation variables. On the other hand, redundant manipulators have more than six joint DOFs. Thus, a redundant manipulator can use more than one joint configuration to establish a desired 6-DOF end effector pose. In other words, additional degrees of freedom can be used to control not just the end effector position and orientation but also the “shape” of the manipulator itself. In addition to the kinematic degrees of freedom, mechanisms may have other DOFs, such as the pivoting lever movement of gripping jaws or scissors blades.
Telerobotic surgery through remote manipulation has been able to reduce the size and number of incisions required in surgery to enhance patient recovery while also helping to reduce patient trauma and discomfort. However, telerobotic surgery has also created many new challenges. Robotic manipulators adjacent the patient have made patient access sometimes difficult for patient-side staff, and for robots designed particularly for single port surgery, access to the single port is of vital importance. For example, a surgeon will typically employ a large number of different surgical instruments/tools during a procedure and ease of access to the manipulator and single port and ease of instrument exchange are highly desirable.
Another challenge results from the fact that a portion of the electromechanical surgical manipulator will be positioned adjacent the operation site. Accordingly, the surgical manipulator may become contaminated during surgery and is typically disposed of or sterilized between operations. From a cost perspective, it would be preferable to sterilize the device. However, the servo motors, sensors, encoders, and electrical connections that are necessary to robotically control the motors typically cannot be sterilized using conventional methods, e.g., steam, heat and pressure, or chemicals, because the system parts would be damaged or destroyed in the sterilization process.
A sterile drape has been previously used to cover the surgical manipulator and has previously included holes through which an adaptor (for example a wrist unit adaptor or a cannula adaptor) would enter the sterile field. However, this disadvantageously requires detachment and sterilization of the adaptors after each procedure and also causes a greater likelihood of contamination through the holes in the drape.
Furthermore, with current sterile drape designs for multi-arm surgical robotic systems, each individual arm of the system is draped, but such designs are not applicable for a single port system, in particular when all the instrument actuators are moved together by a single slave manipulator.
What is needed, therefore, are improved telerobotic systems, apparatus, and methods for remotely controlling surgical instruments at a surgical site on a patient. In particular, these systems, apparatus, and methods should be configured to minimize the need for sterilization to improve cost efficiency while also protecting the system and the surgical patient. In addition, these systems, apparatus, and methods should be designed to minimize instrument exchange time and difficulty during the surgical procedure while offering an accurate interface between the instrument and the manipulator. Furthermore, these systems and apparatus should be configured to minimize form factor so as to provide the most available space around the entry port for surgical staff while also providing for improved range of motion. Furthermore, these systems, apparatus, and methods should provide for organizing, supporting, and efficiently operating multiple instruments through a single port while reducing collisions between instruments and other apparatus.